The postpartum period is accompanied by dramatic changes in hormones and behavior that are critical for reproductive success. In addition to changes in caregiving, pregnancy and the postpartum period are associated with alterations in non-reproductive behaviors, including certain types of learning and memory. Despite these reports, very little, if anything, is known about the neural consequences of motherhood, particularly for brain regions associated with cognitive function. The hippocampus is one such brain region that is also well-recognized for its capacity for structural plasticity. Specifically, various hormonal and experiential factors affect dendritic structure, the number of synapses and the production of new neurons in the hippocampus throughout adulthood. However, no studies to date have investigated the possibility that alterations in structural plasticity occur in the hippocampus during the postpartum period. Thus, the proposed studies will explore the following specific aims: 1) To determine whether structural plasticity in the hippocampus is altered during the postpartum period 2) To evaluate whether hormonal and experiential changes associated with the postpartum period underlie changes in structural plasticity in the hippocampus. [unreadable] [unreadable] [unreadable]